Trough receiver thermal efficiency

Hello,

I'm looking at the effect of receivers with lost vacuum on the solar field thermal performance. When I compare the optical derate and loop thermal efficiency with and without a portion of the field with vacuum loss, the values are the same. All parameters are the same except for the weighting faction. Why don't these values decrease with the addition of receivers with vacuum loss?

Regards,
Pam

Dear Pam,

By default, SAM assumes that a portion of the receivers in the field have vacuum loss: Variation 2, or 1% of the receivers have air in the annulus instead of Hydrogen, and Variation 3, or 0.5% of the receivers have both air in the annulus and broken glass tubes. (Variation 1, or 98.5% of the receivers, are in good condition.) The default values of the parameters reflect the effect of those variations. For Variation 2, the gas in the tube annulus pressure, and estimated average heat loss are for a receiver with vacuum loss. For Variation 3, the absorber absorptance, envelope parameters, gas parameters, heat loss are all for a a receiver with both vacuum loss and broken glass.

When you change the "Variant weighting fraction" for a variation to change the portion of the field with damaged receivers, you should see the weighted heat loss at design and optical derate change.

Are you seeing something different?

Best regards,
Paul.

Dear Pam,

By default, SAM assumes that a portion of the receivers in the field have vacuum loss: Variation 2, or 1% of the receivers have air in the annulus instead of Hydrogen, and Variation 3, or 0.5% of the receivers have both air in the annulus and broken glass tubes. (Variation 1, or 98.5% of the receivers, are in good condition.) The default values of the parameters reflect the effect of those variations. For Variation 2, the gas in the tube annulus pressure, and estimated average heat loss are for a receiver with vacuum loss. For Variation 3, the absorber absorptance, envelope parameters, gas parameters, heat loss are all for a a receiver with both vacuum loss and broken glass.

When you change the "Variant weighting fraction" for a variation to change the portion of the field with damaged receivers, you should see the weighted heat loss at design and optical derate change.

Are you seeing something different?

Best regards,
Paul.